This study is concerned with the design, construction, simulation, and pre-operation of a fluidized-bed reactor for low level radioactive waste treatment by a new chelating resin. In this respect a new mathematical model is suggested to account for the effect of fluid velocity and to determine the key parameters that affect the overall mass transfer. In general, the column height and the diffusion resistance on the resin side control the extent of separation in the reactor. Lowering the particle falling velocity and increasing the column height increase the adsorption extent. The studied variables include the flow rates, feed concentration, column height, working temperature, and pH of the feed solution. Increasing the initial concentration causes the adsorption to increase and the maximum conversion is obtained at the near-neutral condition. Temperature increasing, on the other hand, decreases the adsorption extent. The theoretically calculated results from the mathematical model developed in this study for predicting the conversion extent are found to be in good agreement with the data obtained from the experimental study.